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Twin turbo.....which ones???

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Twin turbo.....which ones???

Post by mrbeige on Tue Oct 21, 2008 5:47 am

Would there be any benefit to running two turbos on a 16v motor? Looking at Rich's RX7 build just got me thinking. Could you run a small turbo then a big turbo (compound), or indeed one turbo per 2 cylinders?

so as not to confine this to 16vs, I've seen twin turbo setups on 24v VRs, so what would be the advantages/disadvantages on the 2.8/2.9 (12/24v) as well?


Last edited by mrbeige on Fri May 29, 2009 7:27 am; edited 2 times in total

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Re: Twin turbo.....which ones???

Post by JNLRacing on Tue Oct 21, 2008 6:53 am

Somepicsof a twin turbo set up on an 8v crossflow longitudinally mounted in my RWD Mk1 that I may get to finish one day

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Long and short if you are going to run 2 turbo's you are best of running 1 per 2 cylinders of identical design and using the intercooler to mix the charge. This way you can get 2 small turbo's to produce 1 bar each giving a compound charge of 2 bar.

The benefits fatter torque curve with quicker spool up providing you get the maths right. Without a restriction of hp at the top end due to a small exhaust housing. Is it worth the hassle if you got the know how it can be fun.

Here's a 1.8t with 2 turbo's recently upgraded the engine and now making 635hp (first car on the page)

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Re: Twin turbo.....which ones???

Post by Flusted on Tue Oct 21, 2008 7:08 am

Holy sh1t
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Re: Twin turbo.....which ones???

Post by dirtytorque on Tue Oct 21, 2008 7:14 am

blimey..
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Re: Twin turbo.....which ones???

Post by mrbeige on Tue Oct 21, 2008 7:20 am

I don't think we should have started this forum, I'm getting silly thoughts now...

I'm liking the quicker spool and fatter torque curve though. Do you think there would be enough room behind a 16v in a Corrado for two turbots? I guess you'd need to calculate the turbo spec based on a 1 litre engine then, given that it each turbo is only driven by 2 cylinders?

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Re: Twin turbo.....which ones???

Post by JNLRacing on Tue Oct 21, 2008 7:42 am

^^^ lol have a look at the pics of the hulsen tuning setup be much the same so will give you a good idea of space

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As for working out the turbo size not as simple as that as you have to keep in account rpm and cylinder head flow not just cc. I opted for 2 x renault 5 T3's. I believe Carlo Hulsen went for a T2 equivalent of a saab originally

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Re: Twin turbo.....which ones???

Post by ctwg60 on Tue Oct 21, 2008 8:36 am

JNLRacing wrote:As for working out the turbo size not as simple as that as you have to keep in account rpm and cylinder head flow not just cc. I opted for 2 x renault 5 T3's. I believe Carlo Hulsen went for a T2 equivalent of a saab originally

What block are you using there then? looks like a 2ltr! And how come you went for 8v xflow? What CR?

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Re: Twin turbo.....which ones???

Post by JNLRacing on Tue Oct 21, 2008 8:39 am

using a bubble block with 1.8KR crank in it. xflow for something different also the fact I could hang 2 turbo's of the side of it. CR is 8.5:1 the idea is to see what a highly tuned 8v was actually capable of reliably.

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Re: Twin turbo.....which ones???

Post by ctwg60 on Tue Oct 21, 2008 8:45 am

Oh right sounds interesting have you used forged pistons? 2 bar sounds like a lot for cast but then you never know what they are capable of when mapped correctly. I'm using cast in my 2ltr 3A counterflow G60 engine and would be interested in your views on cast v forged.

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Re: Twin turbo.....which ones???

Post by mrbeige on Tue Oct 21, 2008 8:49 am

JNLRacing wrote:using a bubble block with 1.8KR crank in it. xflow for something different also the fact I could hang 2 turbo's of the side of it. CR is 8.5:1 the idea is to see what a highly tuned 8v was actually capable of reliably.
I reckon you need to do a build thread study Wink

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Re: Twin turbo.....which ones???

Post by ctwg60 on Tue Oct 21, 2008 8:52 am

mrbeige wrote:
JNLRacing wrote:using a bubble block with 1.8KR crank in it. xflow for something different also the fact I could hang 2 turbo's of the side of it. CR is 8.5:1 the idea is to see what a highly tuned 8v was actually capable of reliably.
I reckon you need to do a build thread study Wink
\

I second that motion. Very Happy

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Re: Twin turbo.....which ones???

Post by JNLRacing on Tue Oct 21, 2008 9:15 am

lol on the build thread it was one of the original build threads on E38 that kicked the trend of on there. The thread fizzled out as I stopped work on it 2 years ago. As business got too busy. It's currently being partially started again as i decided to make some chassis changes to it. It'll be one of those cars that will be done when it is and when it is people will wonder where it came from Wink

However if you are interested I'll post a link in the build thread section to where the photographs of it are up until 2yrs ago.

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Re: Twin turbo.....which ones???

Post by JNLRacing on Tue Oct 21, 2008 9:16 am

As for forged vs cast

Rods are pauters and pistons are forged wiseco's. Personally wouldn't go much above 280hp/tq on cast although 325 has been seen reliably on old yank motors with an additional shot of 250hp of nitrous before the rings let go on one of the cylinders.

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Re: Twin turbo.....which ones???

Post by ctwg60 on Tue Oct 21, 2008 9:53 am

Link would be good. So why the kr crank in a 2ltr? I take it your using 83mm weisco G60 pistons and 136mm length rods?

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Re: Twin turbo.....which ones???

Post by JNLRacing on Tue Oct 21, 2008 1:13 pm

Rods are 144's with custom spec pistons but yes 83mm.

Originally I was going for 2 litres to get some extra torque but once I mathematically worked out the engine flow vs the head flow at different rpm levels I realised that the small capacity increase wasn't going to be worth it and I was better of going solid lifter with a high rpm high lift cam for max power.
As the block was already prept I just changed the crank and ordered the corresponding rods and pistons of my choice.

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Re: Twin turbo.....which ones???

Post by ctwg60 on Tue Oct 21, 2008 2:04 pm

I see, I thought as much. If you go high rpm with 2 bar an extra 100cc is neither hear nor there at 7500rpm+. I understand.

How do you go about balancing the pressures between the turbos? Or is it just a case of joining the outputs and directing the flow to the intercooler?

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Re: Twin turbo.....which ones???

Post by kevhaywire on Wed Oct 22, 2008 7:14 am

I'm a fan of twin turbo on flat and Vee 6s and 8s where you have 2 very defined and seperate turbo banks. Easier plumbing and more exhaust flow for better spool up. But on a 4 pot, I personally don't think the plumbing and other hassle is worth it for the gains, not when a single GT3071R could probably do the same job, if not better.

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Re: Twin turbo.....which ones???

Post by mrbeige on Sun Nov 09, 2008 7:42 am

I'm just thinking of super quick spool, using two smaller turbos with small exhaust A/R maybe

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£300 Corrado 1.8 16v
The good lady wife's Golf VR
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Re: Twin turbo.....which ones???

Post by ctwg60 on Tue Jan 20, 2009 3:57 am

JNLRacing wrote:Somepicsof a twin turbo set up on an 8v crossflow longitudinally mounted in my RWD Mk1 that I may get to finish one day

[You must be registered and logged in to see this image.]

[You must be registered and logged in to see this image.]

Long and short if you are going to run 2 turbo's you are best of running 1 per 2 cylinders of identical design and using the intercooler to mix the charge. This way you can get 2 small turbo's to produce 1 bar each giving a compound charge of 2 bar.

The benefits fatter torque curve with quicker spool up providing you get the maths right. Without a restriction of hp at the top end due to a small exhaust housing. Is it worth the hassle if you got the know how it can be fun.

Here's a 1.8t with 2 turbo's recently upgraded the engine and now making 635hp (first car on the page)

[You must be registered and logged in to see this link.]

So a bit of an off topic thread resurrection but you obviously used a crossflow head to help with the engine bay configuration of twin turbos on a 4 pot but did you flow test the head before and after porting. Is it right that x-flow heads had bigger ports?


Last edited by ctwg60 on Tue Jan 20, 2009 5:59 am; edited 2 times in total

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Re: Twin turbo.....which ones???

Post by dirtytorque on Tue Jan 20, 2009 4:42 am

Also how much does a x-flow head improve breathing other the standard counter flow arrangment in you experience?


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Re: Twin turbo.....which ones???

Post by JNLRacing on Tue Jan 20, 2009 6:40 am

xflow head flows pretty much the same as the rest of the 8v heads. It's just a lot easier when doing turbo, carbs or TB's as you don't get the heatsoak into the intake.

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Re: Twin turbo.....which ones???

Post by mrbeige on Tue Jan 20, 2009 6:43 am

In which case, the X-flow head wont have any huge advantage over the counterflow when retaining the standard charger setup?

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The good lady wife's Golf VR
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Re: Twin turbo.....which ones???

Post by ctwg60 on Tue Jan 20, 2009 6:49 am

Right then! That was easy. Surprised

Why do you think vw did a cross flow 8v? scratch

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Re: Twin turbo.....which ones???

Post by mrbeige on Tue Jan 20, 2009 7:41 am

ctwg60 wrote:Right then! That was easy. Surprised

Why do you think vw did a cross flow 8v? scratch
Packaging I'd imagine, and also variations in performance/economy based on heatsoak. I would guess that all later 8v engines used cross flow.

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£300 Corrado 1.8 16v
The good lady wife's Golf VR
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Re: Twin turbo.....which ones???

Post by ctwg60 on Tue Jan 20, 2009 8:22 am

Yes I came to the same conclusion, it also allowed them to run plastic intakes! Wink The 2.0 xflow engine also produced the same torque and power as the cflow but produced it 800rpm lower for torque and 200rpm lower for power but I think this can be contributed to other changes they made at the same time. So I think I'm not going to be the one to try to disprove anyone by doing a xflow 8v G60 engine.

Oh well my life just got a lot simpler! Smile

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